1. Field of the Invention
The present invention relates to a numerical controller capable of processing an analog signal provided by an analog device and more particularly, to a numerical controller having a built-in sizing means and capable of checking the diameter of a workpiece based upon the analog output signal of an external diameter measuring apparatus.
2. Description of the Prior Art
The conventional numerical controller does not have any sizing function. A separate sizing device is connected through a sequential controller to the numerical controller to enable the numerical controller to execute a sizing function. The sizing device memorizes
data for plural reference sizing points, i.e., points at which the levels of sizing signals are changed, and gives sizing
signals, i.e., on-off signals with binary signal levels, through the sequential controller to the numerical controller to change the operation of the numerical controller. Thus, the sizing function is made possible by additionally providing the numerical controller with the sizing device and the sequential controller.
Accordingly, the conventional controller has a disadvantage that the reference sizing points cannot be adjusted or changed using the control panel of the numerical controller. Namely, the control panel of the sizing device must be operated to ad just the reference sizing points. Further, since the sizing signals applied through the sequential controller to the numerical controller by the sizing device are not analog signals but on-off signals, the numerical controller is unable to carry out a real-time control operation according to an instantaneous diameter value measured by the sizing device.
On the other hand, the measuring head and the amplifier of the sizing device are usually checked before shipment for checking the dependence characteristics of the measuring head and the amplifier of the sizing device on external disturbances, such as temperature variation or mechanical vibrations. This check operation is carried out by connecting a special measuring instrument to the measuring head and the amplifier of the sizing device.
Thus, separate measuring instruments must be connected to the respective functional component units of the sizing device in checking and verifying the characteristics of the sizing device separate from the numerical controller, requiring troublesome work for checking the characteristics. The output of the sizing device is measured independently of the operating condition of the numerically controlled machine tool. Accordingly, it is impossible to evaluate the output characteristics of the sizing device combined with the numerical controller under the condition that the machine tool is being operated under the control of the numerical controller when heat and mechanical vibrations are applied to the sizing device.
On the other hand, there is not any numerical controller capable of changing and selecting a machining process according to the level of an analog signal given thereto by a sizing device, such as a measuring device for measuring the diameter of a workpiece. The sizing device is connected through a sequential controller to the numerical controller. The sizing device converts the analog signal into on-off signals with binary signal levels by comparing the level of the analog signal with reference signal levels and outputs the on-off signals to the numerical controller through the sequential controller. The numerical controller and the sizing device separate from the numerical controller are provided with separate control panels, respectively.
Accordingly, the adjustment of the sizing device, the setting of command values designating the reference signal levels and the change of the number of set reference points (reference levels) can be achieved only by operating the control panel of the sizing device. When a plurality of analog devices are employed other than the sizing device, data must be read on the respective control panels of the separately installed individual analog devices, which further deteriorates working facility.